The present invention relates to fabric softener compositions adapted for the use in the rinse cycle of a laundering process and in particular to concentrated aqueous fabric softener compositions which exhibit stable viscosity characteristics at both low and high ambient temperatures, i.e. such compositions do not increase in viscosity to the point of forming a gel.
Compositions containing quaternary ammonium salts having at least one long chain hydrocarbyl group are commonly used to provide fabric softening benefits when employed in a laundry rinse operation; for example, see U.S. Pat. Nos. 3,349,033; 3,644,203; 3,946,115; 3,997,453; 4,073,735 and 4,119,545.
For most aqueous softener compositions containing cationic quaternary ammonium compounds as active ingredients, the concentration of such cationics has, in general, been limited to the range of about 3 to 6% by weight (see U.S. Pat. No. 3,904,533 and U.S. Pat. No. 3,920,565). Such a low concentration is generally necessitated by the fact that cationics form gels in water systems at concentrations at about above 8%, and while the use of electrolytes to lower the viscosity of such compositions is known (see in particular U.S. Pat. No. 4,199,545), such electrolytes are far from satisfactory from several points of view. On the one hand, from an economics point of view, the use of such electrolytes contributes to the cost of the product and this is generally undesirable. From a functional point of view, the electrolytes often do not perform as required particularly at concentrations of the cationics in the neighborhood of about 12-15%. And finally, while the performance of the electrolytes may mitigate most of the gelling problem, their use is far from satisfactory in providing a highly concentrated aqueous system of cationics which does not gel or severely change in viscosity within the usual range of temperatures encountered in the handling thereof, for example 0.degree. F. (about -18.degree. C.) up to about 140.degree. F. (about 60.degree. C.). In U.S. Pat. No. 3,681,241 a concentrated fabric softening emulsion is described which consists essentially of 3.5 to 6.5 parts by weight of a compound represented for example by distearyl dimethyl ammonium chloride from 3.5 to 6.5 parts by weight of an alkyl amido imidazolinium alkylsulfate and from 0 to 3 parts by weight of a different but similar fatty amido imidazolinium alkylsulfate, the latter allegedly providing low temperature stability for the composition. The total actives contemplated range from about 8 to 13%.
In U.S. Pat. No. 4,155,855, there are described concentrated liquid fabric softeners containing (1) a fabric substantive agent which may be a polyamine, an alkylpyridinium salt or mixture of the two and (2) a fabric softener, in which the polyamines have the formula: ##STR1## wherein R is C.sub.10 to C.sub.24 alkyl or alkenyl or R--O--(CH.sub.2).sub.n --; R.sub.1 may be hydrogen, hydroxyalkoxy groups, C.sub.1 to C.sub.3 alkyl etc.; n is 2 to 6 and m is 1 to 5 and A.sup.(-) represents a charge balancing anion or anions. Among the fabric softeners are alkylimidazolinium salts generally similar to those imidazolinium salts used in the compositions of the present invention. The composition contains 25% to about 55% of an active system of fabric substantive agent and fabric softening component, the former representing 25 to about 85% and the latter 15% to about 75% of the composition. In preferred aspects the fabric substantive component represents from 50 to 85% and preferably 65% to 80% and the softener 15 to 50% and preferable 20 to 35%. In all cases the lowest concentration of the fabric substantive component to the total of this plus softener is given (in terms of percentages) as 25% but based on the ratios of the two agents (6:1 to 1:4) this percentage could conceivably be as low as 20%.